Flexible risers are increasingly in demand mainly for use in marginal offshore fields. The present report addresses a design method for multiple flexible risers installed from an offshore platform in a space efficient manner. The report also describes the analyses and studies conducted to determine optimal values for the various design parameters required for multiple risers system design.
Applications for flexible risers which have recently come into popular use in offshore platforms include use for production, sales, injection, gas lift, and choke lines. In these applications, multiple flexible risers are often suspended from a single point into the sea. It is necessary to keep the adequate riser gaps in order to prevent the interferences, between risers or riser and mooring lines. Therefore, suspended risers will be restricted in number according to the size of platforms. We studied a design method for installing a multiple flexible riser system in order to reduce the Space occupied by the system on the platform deck and achieve efficient installation work and maintenance. The parallel bundle was employed which permits all the risers to be installed at the same time and facilitates maintenance and inspection of each riser after installation. The steep-S multiple riser configuration was adopted to minimize the riser gap and permit the riser bottom position to be fixed.